2:2:4-trimethyl-decahydroquinoline nitrite and carbonate



United States Patent 2,831,861 2:2:4-TR1METHYL-DECAHYDROQUINOLINE NITRITE AND CARBONATE Bertrand Ernest Wilde, Marchwiel, Wrexham, Wales, assignor to Monsanto Chemicals Limited, London, England, a British company No Drawing. Application October 11, 1954 Serial No. 461,679 Claims priority, application Great Britain October 14, 1953 3 Claims. (Cl. 260-286) to the compound 2:2:4-trimethyl-decahydroquinoline,

which has not' previously been described. This compound is capable of forming salts, and it has been found that both the compound itself and its salts are of value in special industrial applications.

zfldifiiii Patented Apr. 22, 1958 sired be used in rubber in conjunction with other antioxicleus by one or more benzyl groups, and they can be ob- The new compounds of the invention are accordingly 2: 2 4-trimethyl-decahydro quinoline.

| CH2 OH It is well known that vulcanised rubber is liable to deteriorate on exposure to the action of heat, light and oxygen-containing gases, and that deterioration occurs in the atmosphere under normal conditions of use. resist this efiect, various substances have been proposed for use in rubber as antioxidants, but many of these sutier from the disadvantage that they cause darkening with time and badly discolour the rubber stocks in which they are incorporated if these should be of a light colour- This problem does not arise with dark-coloured stocks. I

obtained-using carbon blacks, for instance, but it is a serious difiiculty in such compositions as the white rubber stocks obtained using zinc oxide, titanium dioxide and analogous substances.

The discovery has now been made that 2:2:4-trimethyldecahydroquinoline is an effective antioxidant-for rubber,

and moreover that it does not seriously discolourlighb.

coloured rubber stocks, so that by its use the diflicult'ies referred to above can be avoided. It should be mentioned that in determining the effect of rubber antioxidants there are two standard tests, the first being the action of oxygen under pressure on a vulcanised rubber prepared using the antioxidant (the so-called oxygen bomb test) and the second the behaviour of the sample of vulcanised rubber on heating in a hot air oven (the hot air oven test).

above new compound can be demonstrated by both these tests, as is seen from the examples given later in this specification. g v p The 2:2:4-trimethyl-decahydroquinoline may if dc The antioxidant properties of the tained by treating the cresols with benzylating agents such as benzyl chloride. In practice a suitable benzyl cresol for use in the above manner can be obtained by benzylating a commercial cresol containing a mixture of isomers (a so-called cresylic acid) by means of benzyl chloride, preferably so as to introduce on an average about one-benzyl group into each cresol molecule. The product will of course contain a mixture of monobenzyl isomers, in addition to which a small proportion of molecules will be formed containing more than one benzyl group substituted into the nucleus and there will also be a small measure of reaction between the phenolic group and the benzyl chloride to form a benzyl ether. Furthermore, cresylic acids invariably contain a certain proportion of phenols other than the cresols. However, the product will be essentially a mixture of isomeric benzyl cresols and is eminently suitable for use as an antioxidant. Other compounds similar to the benzyl cresols can be i used, for instance benzyl xylenols (and similar benzyl alkyl-phenols) and other benzyl phenols, and these can in general be obtained in an analogous manner.

If a mono-ether of a dihydric phenol is used as a rubber'antioxidant in conjunction with a 2:2:4-trimethyldecahydroquinoline it is preferably the mono-benzyl ether, though other others, for instance the mono-ethyl ether, are also suitable. In practice a mono-ether of a commercial mixture of dihydric phenols is best used,

especially one containing a preponderance of catechol,

and very good results have been obtained using the monoethers, particularly the mono-benzyl ether, of a commercial mixture of dihydric phenols containing about 90% by weight of catechol and methyl-substituted catechols. Other commercial mixtures containing more equal proportions of isomeric dihydric phenols can also be used in forming the ether.

' If a 2:4:6-trialkyl phenol is used a 2:4-dimethyl-6- octyl phenol (especially one obtained by the reaction of 2:4-dimethyl phenol with diisobutylene) is very satisfactory, and other 2:4:6-trialkyl phenols which can be used are 2:6-dimethyl-4-octyl phenol (again one obtained from the dimethyl phenol and diisobutylene is very suitable) and 2:6-dibutyl-4-methyl phenol, in particular where the butyl group is tertiary butyl. It is, however, not necessary to use a pure 2:4:6-trialkyl phenol in preparing mixtures of the above kind, and for instance an alkylated commercial cresylic acid can be used in admixture with the 2:2:4-trimethyl-decahydroquinoline. Thus an octylated cresylic acid obtained by octylating, the acid with diisobutylene can very suitably be used, such an octylated product might contain several isomeric 2:4:6- trialkyl-phenols along with other substances. Where 2:2:4-trimethyl-decahydroquinoline is used as a rubber antioxidant in admixture with another antioxidant the proportions of the constitutents of such mixtures can lie within wide limits. Good results can be obtained using mixtures containing 2:2:4-trimethyl-decahydroquinoline and a second antioxidant in proportions from 25:75 to :25 by weight, and also mixtures outside these limits. Very satisfactory results can be obtained using approximately equal proportions byweightof stock will depend upon the circumstances, but will usually be between 0.005 and 5 parts for each 100parts-of rubber,

and in most instances between 0.25 and 2 parts: In the examples given later in this specification a quantityofil part of antioxidant for each 100 parts of'rubber is used, and good results are obtained with the light-coloured'stock described. It will be appreciated that the antioxidants ot the invention can be, used with dark-coloured rubber stocks also, but they are of particular value with lightcoloured stocks owing to the limited ,numberof satisfactory anitoxidants available which. do not discolour such stocks unduly. They areof value both with natural and synthetic rubber.

It will of course be understood that where a mixture'of. antioxidants is used, the constituents of the mixture may be incorporated in the rubber separately. In general, however, it will be found more convenient to mix the antioxidant constituents together before use.

The salts of 2:2:4-trimethyl-decahydroquinoline can be prepared directly from the base itself, by contacting it with the corresponding acid, or other substance providing the acid radical, and the preparation of the nitrite, carbonate and benzoate is described in the examples given later in this specification.

The salts of 2:2:4-trimethyl-decahydroquinoline, particularly the nitrite and carbonate, are of special use in reducing the tendency of metals to corrode. Thus if the metal object to be protected is placed in an enclosed space together with a quantity ofthesalt, the vapour formed in. the encloscdspace has an efiect in reducing corrosion of the metal. The salts can therefore be described as anti-. corrosives of the vapour'phase inhibitor? type, and they are of particular value where metal objects, are to be:

sealed ,in packages for transport.

A particularly suitable method of operation in-the latter instance is-to incorporate. the salt in the wrapping material, and where this is an absorbent material such as paper it isthen sufficient to treat the wrapping material with an aqueous solution of a suitable Water-soluble salt of 2:2:4-trimethyl-decahydroquinoline and dry. A 5% aqueous solution .of the nitrite of 2:2:4-trirnethyl-decahydroquinoline is very suitable.

The invention. is illustrated by the following examples:-

EXAMPLE] 1 This example describes. thei;preparation of 2:2:4-trimethyl-decahydroquinoline from 2 2 4-trimethyl-l :2-di-' hydroquinoline, from which it .can'readily be obtainedby hydrogenation under pressure. using a nickel catalyst.

The 2:2:4-trimethyl-l :Z-dihydroquinoline itself, the condensation product ofacetoneand aniline, can be obtained by passing acetone vapour into heated aniline in the presence of benzene sulphonic acid, and-separating the product by neutralising thereaction mixture and distilling it at reduced pressure.

600 grams of 2:2:4-trimethyl-l:Z-dihydroquinoline were introduced into a steel autoclave fitted with a rocker mechanism, and a suspension e f-"6 grams otRaney nickelcatalyst in a small amount of ethyl alcohol was added.- The autoclave was closed, and the aircontained in it was replaced by passing a stream of hydrogen through the autoclave.- Thehydrogen pressure in the autoclave was-then increased to 750 pounds per square inch, and-the contents of the autoclave were heated electrically to a temperature of 200 C., the autoclave beingagitated-by means of the' rocker mechanism. The reaction wasthen allowed to proceed, the temperature of the reactants being-maintained at 200 C. and hydroden' under pressure being admitted into'the autoclave from time to time in order to maintain the pressure-at 750 pounds per square inch'-.'-

After-6 hours the amount of hydrogen'whichhad been taken up in the reaction was approximately that required to convert the 2:2:4-trimethyl-1:2-dihydroquinoline to 2:2:4-trimethyl-decahydroquinoline, that is to say 4 molecules of hydrogen for each molecule of the former. The supply of hydrogen was then cut off, the autoclave was allowed to cool to room temperature, and the reaction product was separated from the catalyst by filtration.

The reaction product consisted of 625 grams of a clear colourless liquid which was almost entirely 2:2:4-trimethyl-decahydroquinoline. This couldbe purified further by distillation, to give a. colourless mobile liquid having a boiling point of 232 C. at a pressure of 760 mm. of mercury andarefractive indexof 1.4770 at 25 C.

EXAMPLE:- 2

This. example relatesto. the use as an antioxidant in natural rubber of. the reaction product (almost entirely 222:4 trimethyl decahydroquinoline) obtained asdescribedin Example 1.

A rubber stock of the following composition was compounded on a-laboratory mill:

Parts by weight Pale crepe rubber Blane fixe 50 Zinc oxide 5 Titanium dioxide 5 Stearic acid l Sulphur 2 Accelerator (tetramethyl thiurarn disulphide) 0.375

The stock was first made up without any antioxidant, and then with 1 part by Weight of the reaction product of Example 1.

Each of the two stocks was vulcanised at 126 C. for 20 minutes, and the physical properties of the vulcanised rubbers obtained were determined before ageing and:

(a) After ageing for 6 days at 70 C. in an oxygen bomb at a pressure of 300 lbs./ sq. inch; (b). After ageing for 12 days at 70 C. in a hot air oven.

The conditions of British Standard Specification No. 903/ 1950 were observed.

Thefollowing results were obtained:

Oxygen bomb test (i) TENSION STRENGTH [Kgms./sq. 0th.]

Percent- Original After 6 days age of original figure Stockwithout antioxidant 230 sample melted" Stock with antioxidant 251 149 59 (ii) PERCENTAGE ELONGATION AT BREAK Percent Original After 6 days ago of original figure Stock without antioxidant 685 Sample melted" Stockwlthantioxidant 665 570 86 (iii) MODULUS AT 500% ELONGATION [Kgms./sq. our] Percent- Orlginal Attertidays age of original 7 figure Stock without antioxidant 98 Sample melted" Stock withlantioxidant; 115 96 Hot air oven test (i) TENSION STRENGTH I Pe ce t-. [KgmS-ISQ- Original After a days tie iii 1 original Percent- 5 figure Original After 12 ago of days Stock without antioxidant 685 Sample melted glue Stock with antioxidant 660 570 so Stock without antioxidant 4. 230 86 37 i Stock with antioxidant 251 110 44 m (in) MODULUS AT 500% QLONGATION [Kgms.lsq. 0111.]

(ii) PERCENTAGE ELONGATION AT BREAK I Percent- Original After 6 days age of Percontoriginal Original After 12 age of figure days original 15 figure Stock without antioxidant 98 Sample melted Stock with antioxidant 110 125 111 Stock without antioxidant 685 500 73 t Y stock with antioxidant.-. 665 p 475 71 V Hot air overt test (ill) MODULUS AT 500% ELONGATION I (i) TENSION STRENGTH [Kgms./sq. 0111.] [Kgms./sq. one] Percent- Percent- Origiual After 12 age of Original After 12 age of days original days original figure figure Stock without antioxidant 9s 90 92 Stock without antioxidant- 230 so i 37' a Stock with antioxidant 115 120 104 Stock with antioxidant 237 130 5 5 In order TO test any discolouring effect Of the antioxidant (u PERCENTAGE ELONGATION AT BREAK the two vulcanised stocks were subjected to the action of ultraviolet light for a period of five hours, and their colour, g -at the end of the period was noted, as follows: Original gg gf g Stock without antioxidant Exceedingly pale yellow. .ti e Stock with antioxidant Very slightly more yellow.

Stock without antioxidant. 685 500 73 EXAMPLE 3 Stock with antioxidant can 520 79 The tests carried out in Example 2 Were repeated using m MObULUS AT 500 ELONGATION as antioxidant the same quantity (1 part by weight) of a mixture of equal parts by weight of the reaction product [Kgms'lsq of Example 1 and a benzyl cresol obtained by benzylating a commercial cresylic acid containing about of ortho Original Aft 12 5g cresol, the remainder being largely metaand para-cresols. da s ogiginal It also contained a small proportion of phenol. 5 we The benzyl cresol was prepared as follows. 250 cc. of Stock without antioxidant 98 y 92 the cresylic acid 1n the dry state were placedm a 500 cc. stock with antioxidantnn 117 106 flask fitted with a reflux condenser and heated to C. i 5o 0f Y W i {ldded slowly Over a Once again in order to test any discolouring effect of p f 0f 30 minutes, dufll'lgowhlch m the temperature 50 the antioxidant the two vulcanised stocks were subjected Was {Hereased about h all E benzyl to the action of ultra-violet light for a period of five hours, chloride had been added the heating was discontinued, and and their colour at the end f the Period was noted, as a current of air was blown through the reaction mixture f ll I i for about 30 minutes to remove residual hydrogen chlo- S k h 1 I u ride. The product was then fractionally distilled at a pres- 55 li a fg ff g mg y Pa sure of 12 mm. of mercury; unreacted cresylic acid distoe W1 antloxl ant s y more yel tilled at about 100 C. and the fraction distilling between 1 5911 very P 190 Good 250 C. was collected. This was again frac- EXAMPLE 4 m r ur nd 3 a Pressure of mm of e S y a This example describes the preparation of the nitrite of e fraction distilling between 190 C. and 210 C. col- 60 7.24 p

-tr1metl'iyl-decahydroquinoline. lected. This was the benzyl cresol used as antioxidant, 36 2 i grams of 2.2.4-trimethyl-decahydroquinoline were consisting essentially of a mixture of mono-benzyl isomers issolved in a mixture of 300 cc. of acetone and 3.6 cc. of and containing a little benzyl phenol. d f f d b h The following results were obtained: i an a Hymns Hines (.ggperate y t e i action of glacial acetic acid on sodium nitrite) was passed Oxygen bomb test into the solution. A precipitate wasformed, and when (i) TENSION STRENGTH no further precipitation took place the flow of nitrous [Kgms./sq. 0111.1 fumes was stopped and the precipitate filtered off. It was then washed with a little acetone and dried at 60 C. Percent- The product, the nitrite of 2:2:4-trimethyhdecahydro' Original After 6 days i g gg 70 quinoline, was a pale cream-coloured solid.

figure EXAMPLE 5 stock i h t antioxidant i 230 Sample melted" T example e dascribes the RreRarafion of the Stock with antioxidant 237 182 7 nitnte of 2:2:4-tr1methyl-decahydroquinolme.

Firstly, a solution of the hydrochloride of 2:2:4-tri- I and filtered tocollect the solid product.

methyl-decahydroquinoline was prepared by adding 36.2 grams of' the' amine to adilutesolution of hydrochloric acid'which had been made by dissolving 24 grams of the EXAMPLE 6 This example describes a particularly suitable method Di preparing the nitrite of2:254-trimethyl-decahydroquinoline.

To 1,000 cc. of methanol were added 181 grams of 2:2:4-trimethyl-decahydroquinoline, 76 grams of sodium nitrite and 150 cc. of water, and the mixture was stirred until the solid materials had'dissolv'ed. A solution of 55 grams of 98% sulphuric acid in 55 cc. of water was then added with stirring to the methanol solution. As a're'sult, sodium sulphate was precipitated and the temperature of the mixture rose to 36 C. The mixture was cooled to 24 C. and was filtered to remove the sodium sulphate which was washed'on the filter with 200cc. of

methanol, the washings being added to the main filtrate.

Methanol was then removed from the filtrate by distillation, initially on a water bath at atmospheric pressure and later under reduced pressure; the'volurne of distillate collected being '1,100' cc. To the cold solid residue remaining afterv the distillation were added 250 cc. of benzeneand the mixture was distilled under reflux in a Dean and Stark apparatus to remove water, the total volume of water collected being 30 cc. The residual benzene slurry was then cooled to' 25 C. The latter was washed with 250 cc. of benzene and dried in warm air to yield 162 grams of the nitrite of 2:2:4-trimethyl-decahydroquinoline, a white solid, M. P. 176-179" C. The yield was 71.6% based on the amount of 2:2:4-trimethyldecahydroquinoline used as starting material and practically' all the unreacted amine was recovered.

EXAMPLE 7 This example describes the preparation of: the carbonate.

of 2: 2 4-trirnethyl-decahydroquinoline.

36.2 grams of 2:2:4-trimethyl-decahydroquinoline were dissolved in a mixture of 200 cc. of acetone and 3.6 cc. of water. A stream of carbon dioxide was passed through the solution resulting in the formation of a white precipitate. When no more precipitation took place the flow of carbon dioxide was stopped and the precipitate was filtered otf, washed with a little acetone and dried at room temperature;

The product was the required carbonate, 2. white hygroscopic solid.

EXAMPLE 8 This example describes the preparation of the benzoate of 2:2:4-trimethyl-decahydroquinoline.

6.1 grams of benzoic acid were dissolved in. a mixture of 200 ccof petroleum ether of boiling range 40-60 C. and 100 cc. of-diethyl ether. The solution waswarmed to a temperature of 25 C., and to it was added a solution of 9 grams of 2:2z4-trimethyl-decahydroquinoline in a further 50cc. of the same petroleum ether. A precipitate wasformed, and this was filtered off, washed with a little of the same petroleum ether and dried at 60 C.

The product was a white solid, the required benzoate.

8 EXAMPLE 9 This example and the next relate to the use of the nitrite of Example 4 asa vapour phase corrosion inhibitor.

A number of smalhorown'paper"bagswerethoroughly" soaked in a 5% aqueous solution of the nitrite, excess solution was-drained off, and the bags were allowed to dry in the air. Small pieces of bright mild steel were placed in the bags," which were then closedwith' paper clips and stored outof doors so as to be 'freely' exposedto the atmosphere, though shielded from direct rainfall. A similar series of pieces of bright mild steel were stored in the same way in bags which had not been treated with the 2: 2 4-trimethyl-decahydroquinoline nitrite.

After two weeks ofstorage under these conditions the steel pieces in the untreated bags had rusted badly, but those in the treated bags were still bright and unaffected by rust.

EXAMPLE 10 cc. of a 2% aqueoussolution' of'2z2z4-trirnethyldecahydroquinoline nitritewere placed in each of a number of boiling tubes, and ineachtube a strip of bright mild steel (specially prepared by abrading' with emery paper and degreasing in warm benzene) was suspended in such a way as to avoid condensed water vapour trickling on to it from the boiling tube or the suspending hook. 'A similar series of boiling tubes provided with bright mild. steel strips and containing 50 cc. of water instead of the nitrite solution were prepared as a control. The. tubes were maintained for 14 days in a thermostat at'30"v C. and the mouths of the tubes were opened'for a short time on alternate days to allow the escape of moisture 'vapour.

After 14 days all the steel stripsin the control tubes containing water alone were found to be heavily rusted,

whereas the stripsnsuspended over the 2:2:4-trimethyldecahydroquinoline nitrite solution showed only a slight discolouration.

EXAMPLE 1 1 References Cited in the file of this patent UNITED STATES PATENTS 2,203,899 Dunbrook et a1 June 1.1, 1940 2,251,992 Dickey et al. Aug. 12, 1941 2,290,561 Ingram July 24, 1942 2,514,658 Kehe July 11, 1950 2,582,192 Denison Jan. 8, 1952 2,643,176 Wachter et al. June 23, 1953 2,653,854 Schaar Sept. 29,- 1953 OTHER REFERENCES Braun et al.: Berichte, 1924, vol. 57, p. 388.

Beilstein, Hand. Org. Chem, vol. XX, 2nd suppl. (1953), p. 79citing Yamaguchi'et al., I. Pharm. Soc. Japan. (1926), No. 533, 8.54. 

1. A COMPOUND SELECTED FROM THE CLASS CONSISTING OF 2:2:4-TRIMETHYL-DECAHYDROQUINOLINE NITRITE AND 2:2:4:-TRIMETHYL-DECAHYDROQUINOLINE CARBONATE. 